Cu-Co-Si-Zr ALLOY MATERIAL AND MANUFACTURING METHOD THEREOF

ABSTRACT

The present invention relates to a Cu—Co—Si—Zr alloy material which contains 1.0-2.5 wt % of Co, 0.2-0.7 wt % of Si and 0.001-0.5 wt % of Zr with the elemental ratio Co/Si being 3.5-5.0. The Cu—Co—Si—Zr alloy material contains second phase particles having a diameter of 0.20 μm or more but less than 1.00 μm at a density of 3,000-500,000 particles/mm 2 , and has a crystal grain size of 10 μm or less, an electrical conductivity of 60% IACS or more and good bending workability. The alloy material can be produced by setting the temperature of heating that is carried out after casting and before a solution heat treatment to a temperature that is higher than the later-described solution heat treatment temperature by 45° C. or more, by setting the cooling rate from the start temperature of hot rolling to 600° C. to 100° C./min or less, and by selecting the solution heat treatment temperature from (50× Co wt %+775)° C. to (50× Co wt %+825)° C. (inclusive). The aging treatment after the solution heat treatment is preferably carried out at 450-650° C. for 1-20 hours.

TECHNICAL FIELD

The present invention relates to materials for electronic and electrical equipments having excellent bending workability and being able to show high electrical conductivity, in particular, Cu—Co—Si—Zr copper alloy materials suitable for materials for electronic and electrical equipments such as movable connectors.

BACKGROUND ART

Materials for electronic and electrical equipments require properties such as electrical conductivity, strength, and bending workability, and a demand for materials that allow high current is increasing in recent years for electric and electronic parts, particularly for movable connectors. In order to avoid movable connectors such as floating type connectors becoming larger, a material having good bendability as well as securing high electrical conductivity and strength, even at a thickness of 0.2 mm or more, is necessary.

Conventionally, Cu—Ni—Si, Cu—Co—Si, Cu—Co—Si—Zr, or Cu—Ni—Co—Si copper alloys are known as precipitation strengthened copper alloys having properties that allow for achieving high strength without deteriorating electrical conductivity. In order to manufacture these copper alloys, supplemented element(s) are solutionized by solution treatment, followed by cold rolling and aging treatment to precipitate or crystallize Ni₂Si and Co₂Si etc. as second phase particles in the matrix. However, since the amount of solubility of Ni₂Si is relatively large, it is difficult to achieve an electrical conductivity of 60% IACS or more with a Cu—Ni—Si copper alloy. For this reason, Cu—Co—Si, Cu—Co—Si—Zr or Cu—Ni—Co—Si alloys containing Co₂Si with low amount of solubility as the main precipitate and showing high electrical conductivity are being researched. The target strength cannot be achieved with these copper alloys unless they are sufficiently solutionized first and then precipitated to form fine precipitates. However, because solution treatment at a high temperature will cause coarsening of crystal grains resulting in problems such as deteriorated bending workability, various countermeasures have been investigated.

In Japanese Published Unexamined Patent Application Nos. 2009-242814 (Patent Document 1) and 2008-266787 (Patent Document 2), in order to manufacture a precipitation strengthened copper alloy for materials for electric and electronic parts such as a lead frame, the effect of suppressing crystal grain growth by second phase particles is utilized to control grain size and to improve bending workability. In the above documents, second phase particles precipitate during the cooling process in hot working or the temperature elevation process in solution heat treatment, as well as during the aging treatment after grinding ([0025] in Patent Document 1 etc.) In addition, International Publication No. 2010/016429 (Patent Document 3) discloses Cu—Co—Si(—Zr) alloys with certain compositions in which two types of precipitant with different sizes and compositions exist, leading to the suppression of crystal grain growth and the increase in their strength.

Patent Document 1

-   Japanese Published Unexamined Patent Application No. 2009-242814A

Patent Document 2

-   Japanese Published Unexamined Patent Application No. 2008-266787A

Patent Document 3

-   WO2010/016429

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In general, specific target values for preventing the above movable connectors from becoming larger are an electrical conductivity of 60% IACS or more, and a 0.2% yield strength YS of 600 MPa or more, or a tensile strength TS of 630 MPa or more, as well as the threshold of ratio between the bending radius R and the thickness of material t (MBR/t) without generation of cracks, which is considered an indicator of bending workability, is 0.5 or less (0.3 mm thickness of sheet, Bad Way). This bending workability varies depending on the grain size and the size and number etc. of second phase particles, and the grain size to obtain an MBR/t of 0.5 or less at 0.3 mm plate thickness is thought to be generally 10 μm or less for Cu—Co—Si or Cu—Ni—Co—Si alloys. Crystal grains grow by solution treatment, and thus the grain size is determined by the temperature and time of solution treatment, supplemented element(s), and the size or number of second phase particles.

In Patent Documents 1 and 2, however, Co is not essential and a wide range of second phase particles is targeted. In the method of controlling grain size by second phase particles precipitates described in Patent Document 1, grain size can be controlled but electrical conductivity becomes poor, and high current availability cannot be achieved. Patent Document 2 focuses on second phase particles with diameters of from 50 to 1000 nm as possessing the effect of suppressing the growth of recrystallized grains in solution treatment, but Co second phase particles of this size may sometimes be solutionized and disappear during solution treatment. For this reason, since the temperature and time of solution treatment need to be adjusted so that the precipitates are not solved, only Cu—Co—Si—Zr alloys which are poor in either electrical conductivity or bendability were obtained. In addition, the second phase particles precipitate in this size range may possibly precipitate after solution treatment, and thus it does not show direct controlling effect on grain size. Although the density or diameter and volume density of second phase particles on the crystal grain boundary are evaluated by transmission electron microscope (TEM) observation in the above document, when the second phase was precipitated until grain size could be controlled to 10 μm or less, there was a possibility that accurate values could not be determined due to overlapping of particles and the like.

In addition, although Patent Document 3 focuses on Co second phase particles for the purpose of suppressing crystal grain growth, their grain sizes are 0.005 to 0.05 μm and 0.05 to 0.5 μm in their diameters. The Cu—Co—Si—Zr alloys in this document are inferior to in their bending workability.

As such, because the purpose of conventional precipitation strengthened copper alloys was utilization of thin sheet for electronic parts such as a lead frame, excellent bending workability at a sheet thickness of approximately 0.3 mm has never been developed.

Means for Solving the Problems

The present inventors have performed intensive and extensive research in order to solve the above problems, and attained the following inventions.

(1) A Cu—Co—Si—Zr alloy material with good bending workability wherein said material comprises: 1.0 to 2.5 wt % of Co; 0.2 to 0.7 wt % of Si; and 0.001 to 0.5 wt % of Zr, and wherein a Co/Si elemental ratio is 3.5 to 5.0 and wherein said material contains 3,000 to 500,000 second phase particles per mm² having diameters of from 0.20 μm or more to less than 1.00 μm, and has an electrical conductivity EC of 60% IACS or more, and a grain size of 10 μm or less. (2) The copper alloy material of (1) containing 10 to 2,000 second phase particles per mm² having diameters of from 1.00 μm or more to 10.00 μm or less. (3) The copper alloy material of (1) or (2), wherein the 0.2% yield strength YS is 600 MPa or more. (4) A method of manufacturing the copper alloy material of (1) or (2), wherein the temperature of hot rolling performed after casting and before solution treatment is a temperature that is 45° C. or more higher than the solution treatment temperature selected below, the cooling rate from the temperature at the start of hot rolling to 600° C. is 100° C./min or lower, and the solution treatment temperature is selected from the range of from (50× Co wt %+775)° C. or more to (50× Co wt %+825)° C. or less. (5) The method of manufacturing the copper alloy material of (4), wherein the aging treatment after solution treatment is at 450 to 650° C. for 1 to 20 hours.

In the present invention, the solution treatment temperature is adjusted, the hot heating temperature before solution treatment is also adjusted to be suitable for the solution treatment temperature, and the cooling rate after hot heating is also adjusted to allow precipitation of a particular amount of second phase particles having a particular grain size in order to prevent coarsening of crystal grains in the manufacturing of a Cu—Co—Si—Zr alloy material having a particular composition. Grain size of 10 μm or less can be obtained by adjusting the above second phase particles, and therefore bending workability, electrical conductivity that allows high current as well as practicable strength, suitable for movable connectors can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a reference drawing describing a diameter of a second phase particle.

BEST MODES FOR CARRYING OUT THE INVENTION (Cu—Co—Si—Zr Alloy Material)

The alloy material of the present invention contains 1.0 to 2.5 wt % (hereinafter shown as % unless otherwise indicated), preferably 1.5 to 2.2% of Co, and 0.2 to 0.7%, preferably 0.3 to 0.55% of Si. The remainder other than Zr preferably consists of Cu and unavoidable impurities, but various elements employed by those skilled in the art as components ordinarily added to copper alloys, e.g., Cr, Mg, Mn, Ni, Sn, Zn, P, and Ag etc. within the range that allows achievement of the effect targeted by the constitution of the present invention may be further included.

If second phase particles are Co₂Si, the stoichiometric ratio of Co/Si contained is theoretically 4.2, but is 3.5 to 5.0, preferably 3.8 to 4.6 in the present invention. If the ratio is within these ranges, second phase particles Co₂Si and Co—Si—Zr compound suitable for precipitation strengthening and adjustment of grain size is formed. If Co and/or Si are too low, precipitation strengthening effect will be reduced, and if it is too high, it will not be solutionized and electrical conductivity will also be poor. When second phase particles Co₂Si precipitate, precipitation strengthening effect appears, and the purity of the matrix will increase after precipitation, thus improving electrical conductivity. Further, if a particular amount of second phase particles having a particular size is present, the growth of crystal grains is prevented and the grain size can be made to be 10 μm or less.

An alloy material according to the present invention may contain 0.001 to 0.5 wt % of Zr, preferably 0.01 to 0.4 wt % of Zr, which improves strength and conductivity. These effects are beyond predictions in view of Cu—Co—Si alloy. If the amount of Zr is less than 0.001 wt %, it cannot achieve a desired improvement of strength and conductivity. If the amount of Zr is more than 0.5 wt %, it generates coarse silicides, which deteriorate strength and bending workability.

The grain size of the alloy material of the present invention is 10 μm or less. Ten micrometers or less allows achievement of good bending workability.

The copper alloy material of the present invention may have various shapes, such as for example plates, strips, wires, rods, and foils, and without particular limitation, may be plates or strips for movable connectors.

(Second Phase Particles)

The second phase particles of the present invention refer to particles that generate when other elements are contained in copper to form a phase different from the copper mother phase (matrix). The number of second phase particles having diameters of 50 nm or more is obtained, after mirror finishing by mechanical polishing followed by electrolytic polishing or acid etching, by counting the number of particles having diameters in the corresponding range on a field of a scanning electron microscope photograph obtained by arbitrary five points selection in a cross-section of a copper alloy sheet parallel to rolling direction. The diameter as used herein refers to the average of L1 and L2 as shown in FIG. 1 obtained by measuring the minor axis (L1) and the major axis (L2) of the particle.

Most of the second phase particles of the present invention are Co₂Si and Co—Si—Zr compound, but other intermetallic compounds such as Ni₂Si may also exist as long as the diameter is within the range. Elements that constitute second phase particles can be confirmed for example by using EDX (Energy-Dispersive X-Ray) accompanying FE-SEM (FEI Company Japan, Model XL30SFEG).

The copper alloy material of the present invention contains 3,000 to 500,000/mm², preferably 10,000 to 200,000/mm², and further preferably 13,000 to 100,000/mm² second phase particles having diameters of from 0.20 μm or more to less than 1.00 μm. The particles may precipitate mainly after hot rolling and before solution treatment, but may also precipitate by solution treatment. The second phase particles that precipitated before solution treatment suppress the growth of grain size in solution treatment, but there is also risk of solid solution thereof. Accordingly, it is preferred to adjust the solution treatment conditions to reduce variation in number as much as possible.

In addition, the material preferably comprises 10 to 2,000/mm², further preferably 20 to 1,000/mm², and most preferably 30 to 500/mm² second phase particles having diameters of from 1.00 μm or more to 10.00 μm or less. The cooling rate after hot rolling (hot heating) may be slowed down for precipitation, and first aging treatment can be applied if necessary in order to adjust grain size for the second phase particles. The above preferred range for diameter of the second phase particles is also linked with the number of second phase particles of from 0.20 μm or more to less than 1.00 μm. High temperature solution treatment is possible under the conditions of the above range and the growth of grain size in solution treatment is suppressed, while the sufficiently solutionized Co, Si and Zr are finely precipitated by a later (second) aging treatment, resulting in high strength, high electrical conductivity, and good bending workability to be achieved. However, the number of second phase particles greater than 2,000/mm² is not preferred because bendability will be reduced.

The number of second phase particles having the above diameters of from 0.20 μm or more to less than 1.00 μm and 1.00 μm or more to 10.00 μm or less can be evaluated using a test strip obtained before final rolling or after final working, since the number does not vary considerably before and after solution treatment as well as after second aging treatment.

Precipitation of fine second phase particles is inhibited and precipitation strengthening effect cannot be obtained if second phase particles having diameters greater than 10.00 μm exist. Thus, the number of contained particles having diameters greater than 10.00 μm is preferably 1/mm² or less, further preferably only 0.01/mm² or less.

Although the second phase particles of from 0.05 μm or more to less than 0.20 μm precipitate during hot rolling, the subsequent cooling, and first aging treatment, they are mostly solutionized in solution treatment, and are precipitated by the subsequent cooling and (the second) aging treatment. The second phase particles having diameters of less than 0.05 μm are solutionized in solution treatment, and a large amount thereof is precipitated by (the second) aging treatment. Accordingly, these second phase particles do not show the effect of adjusting grain size, but contribute to improvement in strength.

(Properties of Alloy Material)

The electrical conductivity EC of the alloy material of the present invention is 60% IACS or more, preferably 65% IACS or more. Parts that allow high current can be manufactured when EC is within this range.

Good bending workability as used in the present invention refers to a minimum bending radius MBR/t of 0.5 or less (Bad Way) at 0.3 mm sheet thickness. If MBR/t is 0.5 or less for at 0.3 mm sheet thickness, properties demanded for manufacture and use of electronic parts, in particular movable connectors are fulfilled. Further, better bending workability is obtained when the alloy material of the present invention is made to be thinner than 0.3 mm thickness.

The 0.2% yield strength YS of the alloy material of the present invention is preferably 600 MPa or more, further preferably 650 MPa or more, and the tensile strength TS is preferably 630 MPa or more, further preferably 660 MPa or more. Values within the above range are sufficient especially for electronic parts material such as a plate material for movable connectors.

(Manufacturing Method)

The manufacturing process steps of the alloy material of the present invention are the same or similar to those for an ordinary precipitation strengthened copper alloy, i.e., melt casting->(homogenizing heat treatment)->hot rolling->cooling->(first aging treatment)->grinding->cold rolling->solution treatment->cooling->(cold rolling)->second aging treatment->final cold rolling->(stress relief annealing). Steps in parentheses can be omitted, and final cold rolling may be performed before aging heat treatment.

Although homogenizing heat treatment and hot rolling are performed after casting in the present invention, homogenizing heat treatment may be the heating in hot rolling (in the present specification, heating performed during homogenizing heat treatment and hot rolling is collectively referred to as “hot heating”).

The hot heating temperature may be any temperature at which the supplemented elements mostly solutionize, specifically, it may be a temperature that is 40° C. or more, preferably 45° C. or more higher than the solution treatment temperature selected below. The upper limit of the hot rolling (hot heating) temperature is individually regulated depending on the metal composition and facility, and is ordinarily 1000° C. or less. The heating time will depend on plate thickness, and is preferably 30 to 500 minutes, further preferably 60 to 240 minutes. It is preferred that most of the supplemented elements such as Co or Si solve during hot heating.

The cooling rate after hot rolling is 100° C./min or less, preferably 5 to 50° C./min. With this cooling rate, second phase particles ultimately having diameters of from 0.20 μm or more to less than 10.00 μm will precipitate in the target range. However, only fine second phase particles were conventionally precipitated, since quenching by a water-cooling shower etc. with the aim of suppressing the coarsening of second phase particles.

Materials are ground after cooling, and an arbitrary first aging treatment is preferably further performed to allow adjusting of the target size and number of second phase particles. The conditions for this first aging treatment are preferably at 600 to 800° C. for 30 s to 30 h.

The temperature of solution treatment performed after the above arbitrary first aging treatment is selected from the range of from (50× Co wt %+775)° C. or more to (50× Co wt %+825)° C. or less. The preferred treatment time is 30 to 500 s, further preferably 60 to 200 s. Within this range, the adjusted second phase particles remain resided to prevent the enlargement of grain size, while finely precipitated Co, Si and Zr are sufficiently solutionized and precipitated as fine second phase particles by the later second aging treatment.

The preferred cooling rate after solution treatment is 10° C./s or higher. A cooling rate slower than the above will cause precipitation of second phase particles during cooling, and the amount of solubility will decrease. There is no particularly preferred upper limit for the cooling rate, but e.g. approximately 100° C./s is possible for a generally employed facility.

If the amounts of Co, Si and Zr contained are lower than that in the present invention, or not slowly cooled after hot rolling and second aging treatment heating is not performed, there are only a little second phase particles that are precipitated before solution treatment. When an alloy having only a little precipitated second phase particles is subjected to solution treatment, since an elevated temperature higher than 850° C. for a solution treatment time longer than 1 minute will cause coarsening of grain size, heat treatment can be performed only for a short duration of approximately 30 seconds and the actual solutionizable amount is low, and therefore sufficient precipitation strengthening effect cannot be obtained.

The temperature of second aging treatment after solution treatment is preferably at 450° C. to 650° C. for 1 to 20 hours. Within this range, the diameters of the second phase particles remaining after solution treatment can be maintained within the range of the present invention, as well as the solutionized supplemented elements will precipitate as fine second phase particles and contribute to strength enhancement.

The final rolling reduction ratio is preferably 5 to 40%, further preferably 10 to 20%. A ratio of less than 5% will result in insufficient increase in strength by work hardening, while greater than 40% will result in decrease in bending workability.

Moreover, if final cold rolling is performed before second age treatment, the second age treatment may be performed at 450° C. to 600° C. for 1 to 20 hours.

The stress release annealing temperature is preferably 250 to 600° C., and the annealing time preferably 10 s to 1 hour. Within this range, there is no change in the size and number of second phase particles as well as in grain size.

Examples (Preparation)

To a molten metal made of electrolytic copper, Si, Co and Zr as raw materials, supplementing elements were added varying the amount and type, and the molten metal was casted into an ingot having a thickness of 30 mm. The ingot was heated at the temperature shown in the tables for 3 hours, hot rolled into plates having a thickness of 10 mm. Next, oxyded scales on the surface were ground and removed, subjected to aging treatment for 15 hours and then to solution treatment using appropriately varied temperature and time, cooled at the cooling temperature shown in the tables, subjected to 1 to 15 hours of aging treatment at the temperature shown in the tables, and finished to a final thickness of 0.3 mm by final cold rolling. Stress release annealing time is 1 minute.

(Evaluation)

The concentrations of supplemented elements in the copper alloy matrix were analyzed by ICP-mass spectrometry using samples after the grinding step.

For the diameter and number of second phase particles, a cross-section parallel to the rolling direction of the sample before final cold rolling was mirror finished by means of mechanical polishing, followed by electrolytic polishing or acid etching, and determined from five microscope photographs for each magnification using a scanning electron microscope. Observation magnification is (a) 5×10⁴-power for from 0.05 μm or more to less than 0.20 μm, (b) 1×10⁴-power for from 0.20 μm or more to less than 1.00 μm, and (c) 1×10³-power for from 1.00 μm or more to 10.00 μm or less (each of them is represented as “50-200 nm”, “200-1000 nm” and “1000-10000 nm” respectively in Tables).

For the grain size, average grain size was measured according to JIS H0501 by section method.

For the electrical conductivity EC, specific resistance was measured by a four-terminal method in a thermostatic bath maintained at 20° C. (±0.5° C.) (distance between terminals: 50 mm).

For the bending workability MBR/t, a 90° W bend test (JIS H3130, Bad Way) of short test strips (width 10 mm×length 30 mm×thickness 0.3 mm) taken in T.D. (Transverse Direction) so that the bending axis is perpendicular to the rolling direction was performed, and the minimum bending radius without generation of cracks (mm) was referred to as the MBR (Minimum Bend Radius) and the ratio thereof to the plate thickness t (mm), MBR/t was evaluated.

For the 0.2% yield strength YS and tensile strength TS, sample JIS Z2201-13B size out in the direction parallel to the rolling was measured for three times according to JIS Z 2241, and the average was calculated.

Tables 1A, 1B, and 1C show the result from changes in an additive amount of Zr with the following factors set within the scope of the present invention: a concentration of Co and Si; Co/Si elemental ratio; the number of the second phase particles having diameters of from 0.20 μm or more to less than 1.00 μm; an electrical conductivity EC; and grain size.

Tables 1A and 1B show that comparing to Comparative Example 3 (without Zr), Examples 1 and 2 (with 0.01% of Zr and 0.3% of Zr respectively) showed the increased strength and electrical conductivity or the increased electrical conductivity. In addition, they showed that an electrical conductivity increased in proportion to an additive amount of Zr. However, Comparative Example 4 (with 1.0% of Zr) showed the decreased strength and bending workability (Table 1C is described hereinafter).

Tables 2A, 2B and 2C show the result from changes in the compositions and the manufacturing conditions with an amount of Zr set to 0.1% based on the above results (Table 2C is described hereinafter).

Since Examples 1 to 11 fulfilled the requirements of the present invention, they had excellent properties of an electrical conductivity, strength and bending workability in a thick sheet, which were suitable material for movable connectors allowing high current.

The conditions of Supplementary Example 22 were similar to that of Example 6 but differed in its process as follows: after solution treatment, the material was cooled at the cooling rate according to the table; before aging treatment, the material was finished to a final thickness of 0.3 mm by final cold rolling; the material was subjected to aging treatment at the temperature according to the table for 3 hours; the material was similarly subjected to stress relief annealing. Although the material of Supplementary Example 22 was slightly inferior to Example 6 in its strength, its bending workability was improved.

As for Comparative Example 12, due to high temperature for solution treatment, second phase particles having diameters of from 0.20 μm or more to less than 1.00 μm disappeared during the solution heat treatment, the effect of suppressing crystal grain growth could not be achieved. As a result, the material had a large grain size to be inferior in bending workability.

The material of Comparative Example 13 had low Co/Si ratio. The material of Comparative Example 14 had high Co/Si ratio. Both of them could not benefit from fine second phase particles having the precipitation strengthened effect and thus had low strength. In addition, an electrical conductivity for both of them was inferior due to high solid solute concentration for Co or Si.

As for Comparative Example 15, cooling rate after hot working was slow. Thus, the number of second phase particles having diameters of from 1.00 μm or more to less than 10.00 μm was large. As a result, bending workability was bad.

As for Comparative Example 16, cooling rate after hot working was fast. Thus, the number of second phase particles having diameters of from 0.20 μm or more to less than 1.00 μm was small. Consequently, the material of Comparative Example 16 could not benefit from second phase particles having the effect of suppressing crystal grain growth and thus had bad bending workability. As for Comparative Example 17, cooling rate after hot working was fast. Thus, the number of second phase particles having diameters of from 0.20 μM or more to less than 1.00 μm was small. To compensate for this, the first aging treatment was performed at high temperature resulting in precipitation of second phase particles having diameters of from 0.20 μm or more to less than 1.00 μm. However, this heat treatment made the grain size large. Consequently, bending workability was bad.

As for Comparative Example 18, the temperatures for hot heating and solution treatment were higher than those of Example 8. The effect of suppressing grain growth could not be achieved. Thus, the grain size was large and bending workability was bad. An electrical conductivity was also inferior to Example 8.

As for Comparative Example 19, the temperature for solution treatment was lower than that of Example 11. Thus, an amount of solid solute for additive elements during solution treatment was small. As a result, the strength was low.

As for Comparative Example 20, a concentration of Co was high. The temperature for solution treatment was relatively high and the treatment time was long. Thus, the number of second phase particles having diameters of from 0.20 μm or more to less than 1.00 μm was large and workability was bad.

As for Comparative Example 21, a concentration of Co was high. The temperature for solution treatment was as high as that of hot working. The effect of suppressing grain size could not be achieved. As a result, the number of second phase particles having diameters of from 0.20 μm or more to less than 1.00 μm was small and the number of second phase particles having diameters of from 1.00 μm or more to 10.00 μm or less was large. Thus, bending workability was bad.

Although the present invention is not limited by theory, the relationship between the steps of manufacture and the disappearance and precipitation of second phase particles is thought to be as follows. The supplemented element(s) solutionize into copper during hot heating. Second phase particles having a diameter of 0.05 jam or more will precipitate during hot rolling and in the cooling stage after the hot rolling where the cooling rate is adjusted. In first aging treatment after the hot rolling, second phase particles having a diameter of 0.05 μm or more do not precipitate, while second phase particles having a diameter of less than 0.05 μm precipitate in large amounts. The precipitated second phase particles having a diameter of less than 0.20 μm will disappear by solutionization in solution treatment where the temperature is adjusted. In cooling stage after the solution treatment where cooling rate is adjusted, the second phase particles having a diameter of from 0.05 μm or more to less than 0.2 μm will mainly precipitate in small amounts. In second aging treatment after the solution treatment, second phase particles having a diameter of less than 0.05 μm will precipitate in large amounts.

Tables 1C and 2C show the measurement results about how the second phase particles changed during the manufacturing process which had the following ranges of diameter: (a) from 50 nm or more to less than 200 nm; (b) from 200 nm or more to less than 1000 nm; and (c) from 1000 nm or more to 10000 nm or less. Incidentally, any second phase particles having diameter of more than 10000 nm (10.00 μm) was not observed in all of the measurements. Since the number of second phase particles becomes smaller logarithmically as diameter becomes large, the indicated digits were changed.

Particles (a) solutionized under the solution treatment conditions of the present invention and the number was reduced to approximately one fifth to one tenth, and the number after second aging treatment did not vary relatively. There was almost no increase or decrease in the number of particles (b) under the solution treatment conditions and the second aging treatment conditions of the present invention. There was no change in the number of particles (c) before solution treatment and before final cold rolling under hot heating and cooling conditions of the present invention.

Incidentally, high temperature of first aging treatment increased the number for (b) (see Comparative Example 17). High temperature of or long time of solution treatment tended to decrease the number of (b) to be below the lower limit according to the present invention (see Comparative Examples 18 and 21).

TABLE 1A Cool- Final stress hot 50 × Co wt Solution ing rolling relief Component rolling Cooling Aging % + 775 treatment Rate Aging Reduction annealing CO Si Zr Temp. Rate Temp. Lower limit Temp. Time ° C./ Temp. ratio Temp. wt % wt % wt % Co/Si ° C./3 h ° C./min ° C./15 h ° C. ° C. s sec ° C./1-15 h % ° C./1 min EXP. 1 1.7 0.4 0.01 4.3 980 35 600 860 900 100 20 540 10 500 EXP. 2 1.7 0.4 0.3 4.3 980 35 600 860 900 100 20 540 10 500 COMP. 3 1.7 0.4 0 4.3 980 35 600 860 900 100 20 540 10 500 COMP. 4 1.7 0.4 1.0 4.3 980 35 600 860 900 100 20 540 10 500

TABLE 1B Second phase particles after second aging treatment Mechanical and Physical properties 50-200 nm YS TS EC GS R/t ×1000000/ 200-1000 nm 1000-10000 nm MPa MPa % IACS μm (B.W.) mm² /mm² /mm² EXP. 1 660 680 67 7 0.1 0.5 80,000 120 EXP. 2 650 670 69 6 0.0 0.3 70,000 400 COMP. 3 650 670 66 8 0.2 0.5 18,000 80 COMP. 4 590 610 70 5 1.0 0.1 4,000 2,500

TABLE 1C After first aging treatment, Before first aging treatment before solution treatment After solution treatment grain size 1000- 1000- 1000- After second aging treatment nm 50-200 200-1000 10000 50-200 200-1000 10000 50-200 200-1000 10000 50-200 200-1000 1000-10000 /mm² ×1000000 ×1 ×1 ×1000000 ×1 ×1 ×1000000 ×1 ×1 ×1000000 ×1 ×1 EXP. 1 0 18,000 140 2 22,000 120 0.4 20,000 120 0.5 20,000 120 EXP. 2 0 14,000 400 1.5 16,000 440 0.35 14,000 380 0.3 14,000 400 COMP. 3 0 20,000 80 2.5 22,000 100 0.5 18,000 80 0.5 18,000 80 COMP. 4 0 6,000 2,600 1 4,000 2,500 0.1 4,000 2,600 0.1 4,000 2,500

TABLE 2A Final stress hot 50 × Co wt Solution rolling relief Component rolling Cooling Aging % + 775 treatment Cooling Aging Reduction annealing Co Si Zr Temp. Rate Temp. Lower limit Temp. Time Rate Temp. ratio Temp. wt % wt % wt % Co/Si ° C./3 h ° C./min ° C. ° C. ° C. s ° C./sec ° C. % ° C. EXP. 5 1.5 0.40 0.1 3.8 900 10 600 850 860 100 10 550 10 500 EXP. 6 1.7 0.40 0.1 4.3 980 35 600 860 875 100 20 540 10 500 EXP. 7 1.7 0.40 0.1 4.3 980 35 — 860 875 100 20 540 10 500 EXP. 8 1.9 0.45 0.1 4.2 950 30 600 870 900 100 20 530 10 500 EXP. 9 2.1 0.50 0.1 4.2 975 35 600 880 925 100 20 520 10 500 EXP. 10 2.3 0.46 0.1 5.0 990 40 600 890 940 100 20 510 10 500 EXP. 11 2.5 0.70 0.1 3.6 1000 45 600 900 950 100 10 500 10 500 COMP. 12 1.5 0.36 0.1 4.2 980 35 600 850 930 100 20 550 10 500 COMP. 13 1.7 0.60 0.1 2.8 950 30 600 860 875 100 20 520 10 500 COMP. 14 1.7 0.30 0.1 5.7 950 30 600 860 875 100 20 520 10 500 COMP. 15 1.7 0.40 0.1 4.3 950 3 — 860 875 100 20 520 10 500 COMP. 16 1.7 0.40 0.1 4.3 950 200 650 860 875 100 20 540 10 500 COMP. 17 1.7 0.40 0.1 4.3 950 200 800 860 875 100 20 540 10 500 COMP. 18 1.9 0.45 0.1 4.2 1000 45 600 870 950 100 20 530 10 500 COMP. 19 2.5 0.60 0.1 4.2 1000 45 600 900 800 100 20 510 10 500 COMP. 20 2.7 0.64 0.1 4.2 1000 45 600 910 950 1000 20 500 10 500 COMP. 21 2.7 0.64 0.1 4.2 1000 45 600 910 1000 100 20 500 10 500 SUP. 22 1.7 0.40 0.1 4.3 980 35 600 860 875 100 20 500 10 500

TABLE 2B Second phase particles after second aging treatment Mechanical and Physical properties 50-200 nm YS TS EC GS ×1000000/ 200-1000 nm 1000-10000 nm MPa MPa % IACS μm R/t(B.W.) mm² /mm² /mm² EXP. 5 610 640 69 5 0.0 0.5 20000 140 EXP. 6 650 670 68 7 0.1 0.5 60000 180 EXP. 7 650 680 67 7 0.2 1 80000 180 EXP. 8 660 680 67 7 0.3 1.5 80000 200 EXP. 9 680 710 65 9 0.4 2 140000 300 EXP. 10 730 750 64 10 0.4 3 200000 260 EXP. 11 760 780 62 10 0.4 3 300000 1800 COMP. 12 630 660 67 25 1.5 2 2000 200 COMP. 13 580 620 48 7 0.1 0.2 10000 160 COMP. 14 570 620 58 7 0.1 0.2 8000 140 COMP. 15 620 650 70 7 2.0 0.3 18000 2600 COMP. 16 640 660 67 15 1.0 0.1 2000 100 COMP. 17 630 660 68 20 1.0 1.5 68000 100 COMP. 18 710 740 62 20 1.0 0.2 2000 100 COMP. 19 590 620 70 3 0.5 10 400000 1800 COMP. 20 760 790 63 8 1.0 3 600000 200 COMP. 21 770 800 60 15 2.0 0.1 2000 2100 SUP. 22 610 650 68 7 0.0 0.3 60000 180

TABLE 2C After first aging treatment, Before first aging treatment before solution treatment After solution treatment grain size 1000- 1000- 1000- After second aging treatment nm 50-200 200-1000 10000 50-200 200-1000 10000 50-200 200-1000 10000 50-200 200-1000 1000-10000 /mm² ×1000000 ×1 ×1 ×1000000 ×1 ×1 ×1000000 ×1 ×1 ×1000000 ×1 ×1 EXP. 5 0 14000 120 5 24000 140 0.5 20000 140 0.5 20000 140 EXP. 6 0 70000 180 4 80000 180 0.45 60000 180 0.5 60000 180 EXP. 7 0 80000 180 0 90000 180 0.1 80000 180 0.1 80000 180 EXP. 8 0 70000 200 7 80000 240 1.4 80000 200 1.5 80000 200 EXP. 9 0 160000 300 10 160000 320 1.5 140000 300 2 140000 300 EXP. 10 0 110000 300 15 200000 300 2.5 180000 260 3 200000 260 EXP. 11 0 400000 1800 15 400000 1800 3 300000 1600 3 300000 1800 COMP. 12 0 2000 100 5 2000 180 0.2 2000 200 0.2 2000 200 COMP. 13 0 16000 60 4 16000 160 0.2 10000 160 0.2 10000 160 COMP. 14 0 12000 40 4 12000 120 0.2 8000 140 0.2 8000 140 COMP. 15 0 200000 3000 0 200000 3000 0.3 180000 2600 0.3 180000 2600 COMP. 16 0.8 3000 80 10 4000 80 1 2000 100 1 2000 100 COMP. 17 0.8 3000 80 1 110000 60 0.5 70000 100 0.5 68000 100 COMP. 18 0 18000 100 10 18000 100 0.05 2000 100 0.2 2000 100 COMP. 19 0 400000 1800 15 400000 1800 11 400000 1800 10 400000 1800 COMP. 20 0 600000 240 12 600000 200 3 600000 180 3 600000 200 COMP. 21 0 2000 2400 1.5 4000 2200 0.05 2000 2100 0.1 2000 2100 SUP. 22 0 70000 180 4 80000 180 0.45 60000 180 0.5 60000 180

INDUSTRIAL APPLICABILITY

A copper alloy according to the present invention may achieve practicable strength as well as bending workability suitable for movable connector and electrical conductivity allowing high current.

Explanation of References

-   -   L1: minor axis for particles     -   L2: major axis for particles 

1. A Cu—Co—Si—Zr alloy material with good bending workability wherein said material comprises: 1.0 to 2.5 wt % of Co; 0.2 to 0.7 wt % of Si; and 0.001 to 0.5 wt % of Zr, and wherein a Co/Si elemental ratio is 3.5 to 5.0 and wherein said material contains 3,000 to 500,000 second phase particles per mm² having diameters of from 0.20 μm or more to less than 1.00 μm, and has an electrical conductivity EC of 60% IACS or more, and a grain size of 10 μm or less.
 2. The copper alloy material of claim 1 containing 10 to 2,000 second phase particles per mm² having diameters of from 1.00 μm or more to 10.00 μm or less.
 3. The copper alloy material of claim 1, wherein the 0.2% yield strength YS is 600 MPa or more.
 4. A method of manufacturing the copper alloy material of claim 1, wherein the temperature of hot rolling (hot heating) performed after casting and before solution treatment is a temperature that is 45° C. or more higher than the solution treatment temperature selected below, the cooling rate from the temperature at the start of hot rolling to 600° C. is 100° C./min or lower, and the solution treatment temperature is selected from the range of from (50× Co wt %+775)° C. or more to (50× Co wt %+825)° C. or less.
 5. The method of manufacturing the copper alloy material of claim 4, wherein the aging treatment after solution treatment is at 450 to 650° C. for 1 to 20 hours. 